QoS in MPLS and IP Networks

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MEE 09:

70

Department of Electrical Engineering

School of Engineering

Blekinge Institute of Technology

SE


37 79 Karlskrona

Sweden


Department of Electrical Engineering

School of Engineering

Blekinge Institute of Technology

SE


37 79 Karlskrona

Sweden

Internet

: www.bth.se/tek

Phone

: +46 457 38 50 00

Fax

: + 46 457

279 14

University Supervisor
/ Ex
aminer
:


Alexandru Popescu

alexandru.popescu@bth.se

Department of Telecommunication




University Examiner:


Professor Adrian Popescu

adrian.popescu@bth.se

Depart
ment of Telecommunication


Author(s):


Gull Hussain Sabri

guhu06@student.bth.se



9
th

November
, 2009






QoS in
MPLS and

IP Networks


Master of Electrical Engineering with emphasis in
Telecommunication






1


Abstract



The
thesis
report provides
broad
er

information

about
IP and MPLS technologies and
routing protocols. Internet architecture and problem
s in an IP networks are illustrated
when different internet protocols are
used. Small

focus is provides on the demand
oriented real time applications and data traffic for QoS parameters in IP and MPLS
networks.

Evaluation of
QoS guarantee
parameters such a
s delay, jitter and throughput
are described with state of art study results mainly for
real time applications in IP and
MPLS networks.
Finally MPLS TE implementation and working is described and
proposed to achieve better network performance.




Keywords
:
IP network,
M
PLS

network
, TE
, QoS
.




2


Acknowledgement



I am very thankful to:





ALL Mighty ALLAH for his greatness for blessing me with health and mind.




M
y family

an
d

friends

for

helping me during my degree studies and in hard
times.




My
Telecommunica
tion
thesis supervisor

Mr. Alexandru Popescu at Department
of Telecommunication Systems, Blekinge Tekniska Högskola (BTH), Sweden

for providing me this opportunity to complete master degree

thesis with
complete support and

guidance

during entire period.




M
ikeal Åsman and Lena Magnusson
for
co
mplete assi
stance
in study
throughout
my

master degree.



3

TABLE

OF

CONTENTS


Chapter

1

I
NTRODUCTION



1.1

Infrastructure

…………………………………………………
...
.............
........

9

1.2

Networking
……………………………………………………………………
.

10

1.3

Emerging Technologies
……………………………………………………….

10

1.4

Arpanet

…………………………………………………………
……………..

1
0

1.5

Application Services
…………………………………………………………...

11

1.6

Internet Appl
ications………………………………………………………….
.

1
1

1.7

Problem Definition …………………………………………………………...
.

1
1

1.8

Motivation…………………………………………………………...
.............

12

1.9

Outcomes…………………………………………………………...
...............

1
2

1.10

Thesis Outline
………………………………………………………
...............

1
2




Chapter 2

TECHNICA
L BACKGROUND


2.1

Communication model

…………………………………………………



1
4

2.2

ISP Network

……………………………………………...
...........................

1
5

2.3

Data Transmission Types

……………………………………………………

1
6

2.4

Enterprise Networks

………………………………
…………………………

1
6

2.5

Network Management
………………………
………………………………..

1
7




Chapter 3

MPLS Overview


3.1

MPLS Benefits ……………………………………………………
…………

19

3.1.1

Single Network Structure…………………………………………………...
.

19

3.1.2

IP over MPLS ………………………………………...
..................................

19

3.
1.3

ISP protocol Dependency
…………………………………………………….

2
0

3.
1.4

MPLS VPN Mod
el
……………………………………………………………

2
0

3.
1.5

Traffic Engineering
……………………………………………………………

2
0

3.
2

MPLS Architecture
……………………………………………………………

2
0

3.
2.1

Ingress/Egress Label Switching Router
……………………………………...

2
1

3.
2.2

Intermediate Label Switching Router
…………………………………………

2
1

3.
2.3

Label Switching Paths
………………………………………………………

2
1

3.
2.4

MPLS Label
…………………………………………………………………..

2
2

3.
2.5

Forwards Equivalency Class
…………………………………………………

2
3

3.
2.6

LSR Operational Model
………………………………………………………

2
3

3.
3

MPLS Label Packet Forwarding
……………………………
………………..

2
4

3.
4

Cisco Express Forwarding
……………………………………………………

2
6

3.
4.1

Process Switching
…………………………………………………………….

2
6

3.
4.2

Fast Switching
………………………………………………………………..

2
7

3.
5

Traffic
Engineering in

MPLS
………………………………………………..

28

3.
6

MPLS TE Operations
………………………
………………………………..

29

3.
6.1

Link Information Distribution
……………………………………………….

29

3.
6.2

Computing Paths
……………………………………………………………..

29



4

3.
6.3

TE LSPs Signalling
……………………………………………………………

3
0

3.
7

Basic MPLS Device and Interfaces
…………………………………………..

3
0

3.
8

MPLS Operati
onal Modes
……………………………………………………

3
0




Chapter 4

IP NETWORKS


4.1

IP Standard Architecture

………………………………………
…………….

3
3

4.2

Internet Protocol
……………………………………………………………..

3
5

4.
2.1

Datagram Fragmentation/Defragmentation
…………………………………

3
5

4.
2.2

IP Header

………………………
………………………………
……………

3
6

4.
3

Intranet work Routing Communication
……………………………
………..

3
7

4.
4

Routing Information Protocol

……………………………………………...
.

3
8

4.
5

OSPF Protocol

………………………………………………
………………

39

4.
5.1

Distance Vector Algorithm Versus Link State Algorithm


…………….

4
0

4.
5.2

OSPF Packet
…………………………………………………
………………

4
1

4.
6

Exterior Gateway Protocol

……………………………………………
…….

4
2

4.
7

Border Gateway Protocol
….
………………………………………………...

4
3




Chapter 5

ROUTING PROTOCOLS AND MECHANISM
.


5.1

MPLS Protocols

……………
……………………..
…………………………

4
5

5.
2

MPLS Routing Protocols

……………………………………………………

4
5

5.
3

MPLS Signalling Protocols

………………………

………………………..

4
5

5.
4

Label
D
istribution Protocol
…………………………
……..
…………………

4
5

5.
4.1

Version

……………………………………………………

………………..

4
6

5.4.2

PDU Length
……………………………………………………………
……..

4
7

5.4.3

LDP Identifier
…………………………………………………
………………

4
7

5.4.4

LDP Messages
…………………………………………………………………

4
7

5.5

LDP Messages Exchange
M
echanism
……
….
……………………………….

49

5.5.1

Discovery Message
……………………………………………………………

49

5.5.2

Session Message
……………………………
.
…………………
……………..

49

5.5.3

Advertisement Message
………………………………………………………

49

5
.5
.
4

Notification Message

………………………………………………………


5
0

5.
6

Resource Reservation Protocol
………………………………………………
.

5
0

5.
7

Transmission Control Protocol
……………………………………………
….

5
2

5.
8

User Datagram Proto
col
…………………………………………………
……

5
2




Chapter 6

QoS
IN IP/MPLS NETWORKS


6.1

Best Effort Service Model …………………………………………………...
..

5
6

6.
2

Integrated Service Model ……………………………………………………
..

5
6

6.
2.1

Class of Service……………………………………………………………
…..

5
6

6.
2.2

Control Mecha
nism………………………………………………………
…..

5
7

6.
3

Differential Service Model …………………………………………………


5
7

6.4

Benefits of QoS
……………………………………………………………….

5
9

6.5

QoS in IP Networks …………..…………………………………...................

59



5

6.5.1

Integrated Service Model for IP …………..……………………
……………..

60

6.5.2

Differentiated Service Model for IP …………..………………………………

61

6.
6

QoS in MPLS Networks …………..
…………………………………...
...........

6
3




Chapter
7

MPLS TRAFFIC ENGINEERING AND VPN


7
.
1

MPLS Traffic Engineering……………………………………………………
.

70

7
.
2

Traffic
Engineering Basic
……………………………………………………..

70

7
.
3

MPLS Traffic Engineering Overview
…………………………………………

71

7
.
4

RSVP with Traffic Engineering Extension

……………………
……………..

71

7
.
4.1

RSVP Path Message

…………………………………………………...
..........

71

7
.
4.2

RSVP Reservation Messag
e

………………………………………………
….

72

7
.
4.3

RSVP Error Message

………………………………………………………
….

72

7
.
4.4

RSVP Tear Message

………………………………………………………
…..

73

7
.
5

MPLS VPN Networks
……………………………………………………
……

73

7
.
6

Definition of VPN
……………………………………………………………..

73

7
.
7

Advantages of MPLS V
PN over Other Technologies
………………………...

74

7
.
8

Kinds of MPLS Based VPN
…………………………………………………
..

75

7
.
9

Security Connection in MPLS Under the Circumstances of VPN
……………

7
6

7
.
9.1

Virtual Routing Forwarding
…………………………………………………..

7
7

7
.
9.2

Routing Distinguisher
………
………………………………………………...

7
7

7
.
9.3

Route Targets
………………………………………………………………….

7
8




Chapter 8

COMPARISON

AND ANALYSIS

OF IP/ MPLS

NETWORKS


8.1

Functionality
………………………………………………………………….

80

8.2

Multimedia Application
………………………………………………………

80

8.3

QoS in IP/MPLS

…………………………………………………………..

82

8.4

Performance Parameters
……………………………………………………..

84

8.5

Traffic Engineering
……………………………………………
…………….

84

8.6

Security Issues
…………………………………………………………
…….

84

8.7

GMPLS……....……………………………………………………………….

85




Chapter 9

CONCLUSION AND
FUTURE WORK


9.1

Conclusion……………………………………………………………………

87

9.2

Future Work…………………………………………………………………

88





REFERENCE ……………………………………………………………….

89






6

List of Abbreviations


Acronym

Description

ARP

Automatic Repeat Request

ATM

Asynchro
no
us Transfer Mo
de

BGP

Boarder gate Way Protocol

BoS

Bottom of Stack

CBR

Constant Bit Rate

CEF

Cisco Express Forwarding

CRC

Cyclic
redundancy

Check

DV

Distance Vector

DBMS

Data Base Management System

EGP

E
xterior

gateway Protocol

EIGRP

Enhanced Interior gateway
Routing Protocol

FEC

Forward Error Correction

FTP

File Transfer protocol

GWT

Google wireless Transponder

ISP

Internet Service provider

IP

Internet Protocol

IOS

Internet Operating System

IGP

Interior gateway Protocol

ISIS

Intermediate system to in
termediate system

IPTV

Internet protocol television

IPV4

Internet protocol version4

ITU

International

Telecommunication Unit

IHL

Internet Header Length

IETF

Internet Engineering Task Force

IBM

International Business Machines

ISDN

Integrated service
Digital Network

LAN

Local Area Network

LDP

Label Distribution Protocol

LSR

Label

Switch

Router

LSP

Label
Switch

Path

LFIB

Label Forwarding Information Base

MPLS

Multiprotocol

Label Switching



7

MAN

Metropolitan Area Network

MTU

Maximum

Transmission U
nit

MAC

Medium Access Control

MIB

Management Information Base

NMS

Network
Monitoring

System

NAT

Network

Address Translation

NOC

Network Operation
Centre

OSI

Open System Interconnection

OSPF

Open Shortest Path First

OAM

Object Access
Method

PDU

Pac
ket Distribution Unit

PVC

Permanent virtual circuit

PHB

Per Hop
Behaviour

POP

Point of Presence

PSTN

Public
Switch

Telephone Network

PPP

Point to Point Protocol

PDU

Packet Distribution Unit

QoS

Quality of Service

RSVP

Resource Reservation Control P
rotocol

RIP

Routing Information Protocol

SMS

Short Message Service

SNMP

Simple Network
Management

protocol

SLA

Service Level
Agreement

TE

Traffic Engineering

TCP

Transmission Control protocol

TTL

Time to Live

LIB

Label Information Base

TDM

Time
Division Multiplexing

TDP

Tag Distribution Protocol

TOS

Type of Service

VLAN

Virtual Local Area Network

VOIP

Voice Over Internet Protocol

VPN

Virtual Private
Network



8



Chapter 1

Introduction




9


Internet is an immense

network

and surrounds many
netwo
rk technologies, the
existence of the
Linux OS adheres esteems pioneer technology generation in the
beginning.
Linux

technology was complex, but better and faster than the other
competitors at the time. Linux innovation ideas embark the software developmen
t
industry and the focus software’s consists and required for financial and economic
transactions. This development phases lead the technology orientations to focus on
transmission connectivity of the systems terms as data communication in a large scale
so

the meaning of the transactions and the lift
boundless

withdraws and the uniqueness
of the
network should form
.


Linux built the internet though innovations of economic theories, since the many
developers, businesses, corporations, governments, etc requi
re it to deploy t
he Linux
systems and make them operate able. Considering economy as a global internet and
software enable and driven technology comprised of human cognitive
speculations, we
analyze the concepts for acceptance and credibility for learning
the features and utilities
in an internet development. Clearly, internet invent innovation lies ahead of any
invention that causes to ultimate development but instead internet develop through
innovative research consequences for better utilization of syste
ms and incorporating
technology standards.


Looking at the internet we see and unclear picture of data communication networks
where the sources are attached at
either side or

destinations on the other side while the
communication channel between them form
s an internet itself. Focusing on the
communication channel except complexities present at either sides of source and
destinations, application and protocol involved in data communication, we extremely
encircle the communication channel that comprises of n
etwork or internet i.e. bridges
and routers, but mainly routers in this thesis. The creation of World Wide Web (www
)
was

existed through Ted Nelson’s [1] ideas of 37 years of struggle with Tim Berner Lee
as a first WWW programmer with the possibility of Ne
XT computers having the
support
of http

and internet applications.


Existence of internet at the beginning was moreover illusionary concepts of use but
current internet infrastructure and technology emergence make it possible to connect
billions of users
thousands of miles away with variety of impossible contents, multiple
groups having discussions, businesses connecting through
virtual connections, with
multiple applications running at the nodes and transmitting different types of data.
An
idea of digital

packet switched network for the message delivery between telegraph was
studied in 1850s. At that time telegraph, telex and telephony were key developing
technologies

that make internet possible through characteristics. There are certain
paradigms to consi
der
knowing

the reality behind internet.


1.1

INFRASTRUCTURE



In U.S telegraph networks started in early 1850s and quickly encompassing majority of
the big cities while deploying first electronic and messaging comm
unication systems

[2]
. With an increase in t
he connections, intermediate telegraph offices become dense
and main offices formed into switching cente
rs. Messages from the either side arrived at
a wire or pneumatic tube where they were sorted and forwarded based on some tube
system. Around 450 telegra
phs were deployed in London that was connected through


10

68 tubes, so the main office in New York was running that tube system. Soon the
problem of increased traffic followed the concentration to find telegraphy bottlenecks.
An enormous effort was made by sk
illed operators having expertise in morse code,
Charles Wheatstone who developed ABC telegraph and provided solution at that time.
It was a solution that opened many questions a
nd problems arising afterwards and then
the solutions leading towards innovativ
e internet.


1.2

NETWORKING


The term is based on telegraphy and until 19
th

century
,

some sort of communication
infrastructure was developed through Graham Bell’s invention

[2]
.

However, it was
small distance communication system with low data capacity connect
ions. In case of
increase in the distance, fading was observed. Maxwell’s equations
helped to

design
systems that were capable of transmitting electronic signals i.e. speech with higher
distances. Through the improvement of communication medium i.e. twiste
d pair and
coaxial cables, it became possible to achieve higher data rates and possibly television
broadcasting was made possible.


1.3

EMERGING

TECHNOLOGIES


In 19
th

century telephone became internationally available which caused telegraphy and
telex service
s to reduce, as a result businesses required to adopt new technology to save
the businesses and operators. Teletype captured the world of newspapers

while Telex
acted as a news service and their integration and improvements in the production
provided promi
sing results for commercial news operators. Since high accuracy and
availability was required for telegraph lines to become highly acceptable so any quality
constraints caused due to rain and high traffic increases the probability of errors. With
the innov
ative hit and trial mechanism certain loopholes were eradicated but the
development was very slow and telegraphs

businesses wanted a change for quality,
accuracy, availability and acceptability of communication medium that was even harder
for Morse operato
rs to provide. However research process and business innovation
causes rapid changes in the system improvements and a company called Morkrum
established facilities to provide and fulfill commercial telegrams..



Looking closely at telephone, telegraphy, fa
x, telex and computer networks as a
communication medium are not identical. Every technology has different mode of
operation and communication mechanism. Telephony mainly provides an infrastructure
for communication mechanism between businesses or an indiv
idual while telex
provide
d

financial transactions in global organizations.
Internet is considered as a
research network, the history of data communication and networks without having
cognitive reasons for computer applications.



1.4

ARPANET


The idea was prop
osed to
Lawrence
Robert and soon work was started to develop an
interface message processor to connect interface machines by forming a simple network
which was successfully implemented by ARPANET. Connectivity was made between
four nodes and an extension w
as provided by Robert up till 15 n
odes and so one with
possible implementations
and deployments at research and military sites. Network


11

Analysis Corporation was formed for planning the network and its operations to keep
the network running. Future extensio
ns lead the network at current stage.


1.5

APPLICATION SERVICES


Dynamic growth in internet causes the mind to reflect the ideas meant possible with
involvement of internet technology

while b
usinesses
are

envisioning a radical change in
the society and to com
pete in the world through technology orientation,

so

they develop
some goals and objectives. The businesses should have computation capabilities, text
editing possibilities, services to provide solutions to the problems,
keeping records,
establishing commu
nication with business partners, reliable financial transactions, sale
and purchase options, obtaining remote access to the information, etc. These application
services were very early to point since the existing of new technologies required
decades to ful
fill the gap and develop them for market acceptability

[3]
.


1.6

INTERNET APPLICATIONS


These are basically
rich internet appli
cations i.e. client server and
web application
running on the network nodes under standard web browsers. It includes frameworks,
plu
g
-
ins, sandboxes and virtual machines sometimes dependent on Adobe Flash, Java,
GWT etc features to run these applications.
These applications are installed and running
on rich clients or web client connected to the internet, sometimes these clients requir
e
VPN, CITRIX Hosting for server security

[3]
.

YouTube
, online gaming and other
application servers on the telecommunication network are good examples
.


Internet
traffic depends of the internet applications i.e. r
eal time applications require
quality of se
rvice guarantee
and thus generate more traffic.
The core network consist of
fiber optic medium that connects the seven continents and have much higher bandwidth
to manage higher data rates

connecting the ISPs. Moreover, ISPs connecting home
businesses and
corporate networks offer less bandwidth that causes increased
congestion and network load at their networks.



1.7

PROBLEM DEFINITION


Internet lies through a network of interconnected nodes that transmit data through
switching mechanism
. Internet core
routers

connect and forms an internet through some
communication mechanism i.e. protocols
. A
lthough OSI reference model and TCP/IP
had been successful in early stages of implementation for reliable and efficient data
transmission but with
the development of
heavy

applications at the network nodes the
bandwidth requirement is increased or the QoS is demand oriented

[4
-
5]
. It is however
probable for the traditional internet protocols to transmit higher quality data at a higher
rate as compared to normal text data pa
ckets. Real time applications demand for higher
bandwidth and QoS guarantees and to be able to keep the businesses running,
researcher are struggling to figure the solution to categorize and implement the routing
protocols that separate the class of servic
es at the core network.


MPLS is one solution to the existing
problem;

it not only takes different paths to avoid
congestion, but uses label switched technology to efficiently deliver the packets through
MPLS network.

The thesis will focus on different ty
pe of applications that require QoS


12

guarantee, design, development and implementation of MPLS networks,

architecture,
characteristics and effects in comparison to traditional IP networ
ks.



1.8

MOTIVATION


MPLS is a new technology for design and implementa
tion of reliable, sec
ure, efficient
and standard

QoS

services and application classes. This technology will have lasting
solutions for traffic engineering, VPN tunneling, multicasting etc. The technology itself
is the necessity of the current ISP stack hol
ders. There will be more possible research in
the development and advancement in its routing protocols and security features. MPLS
will work efficiently in telecom industry since Nokia, Siemens,
Ericsson;

Apple etc are
developing real time applications for

mobile nodes in the horizons for internet
connectivity had already been implemented through third generation
telecommunication. IPTV is a real time application that requires extremely high quality
of service and depends on the network traffic for efficien
t and reliable video packet data
transfer over the internet. Since demand for the QoS applications increases so
it
ultimately
affects

internet and its solutions posed by MPLS network for bandwidth
utilization through traffic engineering and optimization

[4
-
5]
.


1.9

OUTCOMES


The thesis main contribution will comprise of state of the art study to compare IP
networks with MPLS networks in terms of different routing protocols. The study will
provide better understanding and learning concepts for the beginners
, information
regarding MPLS importance, uses and deployment for the businesses. This study will
help me to develop solid theoretical background for industrial projects in MPLS.



1.10

THESIS OUTLINE


Introduction
is
chapter
1

that
provides detail descripti
on about internet development
as

an innovation

process, problem definition, motivation and expected outcomes. Chapter

2 give technical background information about the communication network and
technologies. Chapter 3
describe an
overview of MPLS

technolog
y, M
PLS architecture
and its components
,
MPLS working, applications,
MPLS label, components, LSPs and
relevant material along with

traffic engineering
, VPN

and QoS services.

Chapter
4

discuss
an
overview of IP network, architecture description, internet pr
otocols, QoS
parameters, problems in IP network and required solutions
. Chapter
5

explains
fundamental
IP and MPLS
routing
protocols

and routing mechanisms.

Chapter
6

discuss
QoS issues in MPLS, class of services, service level agreement and the need for Q
oS.

Chapter
7 describe
MPLS

Traffic Engineering concepts and VPN implementation.
Chapter
8

is based on an analytical study for comparing

of
IP and MPLS networks.

Finally chapter 9

provides conclusions and

future work
based upon comparison study.



13






Chap
ter 2

Technical

Background




14

In this chapter we will discusses data communication, protocols, IP network
infrastructure, application types, MPLS advantages and traffic engineering concepts.


2.1

Communication Model

In digital communication world packets a
re transmitted from source to destination, the
channel called as transmission system is present in the central between source and
destination. Source generates and transmits data packets towards destination through
destination IP address, the transmission
system consist of no. of hops from source to
destination

[1]
.


















Figure 2
.
1
: Communication Model


Above figure is a simplified communication model
consisting

of source transmission
system and destination .Transmission system could be WAN, M
AN, or LAN network of
interconnected devices.



A
protocol

is required to perform communication between these devices and end nodes
.
These end nods may contain FTP applications, DBMS, any web browser, financial
software or specialized game applications req
uiring and internet connect activity to
establish Client
-
Server access mechanism through protocols. In general communication
comprises of three layer model
is applied [6]
i.e. Network Access layer, Transport layer,
Application layer which surrounds applica
tions, computers and network involved in
TRANSMIISION

DESTINATION

HOP 3

Switching Node

Local Area Nw
Network



15

communication system.

OSI is seven layers standard model for data communication but
mainly TCP/IP five layers model is implemented in an internet
.


Packet Switching Technology was emerged due to bottlenecks in the c
ircuit switching
technology to carry voice data for telecommunication networks. Since circuit switching
networks must have dedicated connection for voice data and the availability of
resources was limited as well as resource utilization
was low, packet swi
tching
technology was developed to overcome problems associated with voice data packets.
Also circuit switching only offers constant data rate while packet switching performs
data transmission in small
packets. In case of larger packets inter connected dev
ice
performs fragmentation and defragmentation at either transmission nodes
. Packet
switching
technology reduces

propagation delay, transmission time, node delay, and
thus increasing transmission per
formance over circuit switching technology.



Protocols a
re principally required to performs manipulation on incoming data packet
from the source the and forward it to desired destination .This
involves routing
operation for
required key
protocol

characterises to be considered for
implementation.
The routing fun
ction/algorithm must contain simplicity, efficiency, accuracy, stability,
robustness, optimality and other routing
functionality
.


2.2

ISP Network

Internet service provider connects homes, enterprise business, and other ISPs and
consists of multiple point

of presence (POP) depending upon on ISPs size.
POP
topology consist
core

routers which are high speed traffic trunks connected through
fibre optic transmission medium and connects other ISPs.

Border routers lie on the edge
of ISPs network connecting other

ISPs while service routers like web hosting
application servers are present are within ISPs networks that connect difference
application server
.ISP provide four types of connections

[7]
.


a)

Low speed connection with low band width, huge no of users, an ofte
n with less
revenue generation capabilities i.e. Dialup PSTN and ISDN.

b)

Medium speed connection also low band width, acceptable no of users, and
56/64K lines.

c)

High speed connection like E1++ data rate are implemented for medium band
width requirements and
decrease no of users.

d)

Broad band connection are cable wireless are xDSL connection with higher band
width requirements facilitate large no of users.



Network operation centre (NOC
) Module

performs backups, network monitoring and
analysis, log

management a
nd security management.

NOC modules implement interior


16

gate way protocol i.e. ISIS, EIGRP and OSPF to provide point to point links. An
exterior gateway protocol i.e. BGP or EGP is implemented to establish customer prefix
and manage internet routes.


2.3

DA
TA TRANSMISSION
TYPES


Internet implements

packet switching technology where all the packets are provided
with IP addresses. The MTU size is 1500 bytes that

carries all types of application data
i.e.
data;

voice and video which is also termed as triple pl
ay technology. Certain
problem in IP network are describe in later chapter however IP packet carrying data
performance is efficient as compare to voice and video data. UDP and TCP protocols
are mainly used for different data types while TCP provides conne
ction oriented data
transmission instead of UDP connectionless data transmission. Routing protocols
running on different hops in an internet infrastructure performs destination address
traversing by allowing shortest path towards IP destination address. Ma
inly it reduces
performance if congestion happens at shortest path while TCP tries to make slow start
to keep the link active, and due to some unutilized paths. MPLS make use of label
technology to limit these problems.


IP traffic can also manage voice an
d video data until
less user traffic exists but as soon
as the traffic increases through user request the packets travelling the same IP
destination path become lost or slow due to OSPF congestion. So the quality of service
guarantee voice and video data i
s no more accomplished.

There is no standard way to
provide QoS to voice and video data packets in IP packet transmission. MPLS describes
separate quality of services classes at LSR to priorities data packet passing through its
network.


Mainly three types

of application data is used on computer nodes as well as in data
traffic. Email, www, spreadsheets are all examples of data traffic type. Current
multimedia services running at computer application need to have reliable real time
traffic flows between sou
rce and destination to be able to avoid delay and packet loss.


2
.4

ENTERPRISE NETWORK


Enterprise networks are similar to ISP except it provides connectivity to financial
organisation, government sector, multinational organisation and health care orga
nisation
etc.

W
AN is an example of large enterprise network connecting branch offices at
different location of the world.
These networks comprise of legacy equipment which are
difficult to manage spread around large geographical area.

Enterprise network of
fer
telecommunication and data transmission services to their clients i.e. print, email


17

accounts, data storing and sharing capabilities, share application access, intranet,
internet, extranet, ecommerce, voice and video dialling and connectivity through IP

technology, VLAN and VPNs, recovery management system and many more. The
network is utilized for better business transaction, saving cost through VOIP solutions
and reducing telecom traffic carriers. Enterprise networks are capable of supporting
different

devices and services which increase access flexibility.
Internet facilitates

enterprise information among company employees for posting different announcement
to all the employees.

Main issues in enterprise networks are unavailability of resources
when de
vices become offline, capacity requirements, and traffic performance decrease.
Thus we require network operations to be working and the business process to continue
without any errors and problems.


2
.5 NETWORK MANAGEMENT


Networks management
requires
managing enterprise
,

ISPs and MPLS networks
through
network management
applications.

Although intelligent switch, routers and other
network devices are deployed on the network but still proper configuration is required
and a system is suppose to be develop

to dissolve any device failures. NMS have
complete overview of the network manage record and audit files, help network, help
traffic engineering, modelling, planning, backup configuration, quality of service
provisioning etc effectively.
SNMP V3 is curren
tly used to configure devices on the
network, extract information regarding fault, configuration, accounting, performance
and security (FCAPS). The goal of NMS mainly concerns about any fault, event or
alarms notification.


In MPLS network management addre
sses Management Information Base (MIB) and its
elements to make MPLS network operation

[8]
. MPLS LSR MIB and MPLS TE MIB
are two MIBs describe by IETF standard. They aim to obtain management of low level
MPLS objects i.e. table segment interfaces and cross

connect, high level MPLS objects
i.e.
resource blocks,
EROs
and
traffic tunnels

and

creation of LSPs
.

LSR MIB include
MPLS interface configuration, in/out segment, label stack, traffic, performance
parameter and cross connects. TE MIB object consist of TE

tunnel resources
/ path/ and
performance counters.



18





Chapter
3

MPLS Overview and
Architecture


19


MPLS is evolved through ATM and frame relay VAN networks; MPLS uses labels to
advertise between different routers by means of label mapping through label swit
ching
mechanism. Previously frame relay uses frames while ATM uses cells to map labels, to
label switching techniques, frames cannot be of fix length while the cells consists of fix
length with 5 bytes of header and 48 bytes of payload. ATM and frame relay

are
identical in a way when label traversing each hop in the network causes the label to
change the header value. This differentiate from the traditional IP network when IP
packets are forwarded through router it does not change the value at the header of

the IP
packet i.e. destination IP address. MPLS also adds the label at the ingress Label Edge
Router (LER) of the MPLS network, changes the label value at each LER within MPLS
network until it reaches the egress LER, where completely removes the MPLS labe
l and
the data packet is forwarded towards destination IP address

[5]
.


The reason for implementing IP technology in early stage was such that label switching
technology was slower and routers forward the IP packets toward the destination IP
address by lo
oking at the IP header and finding exact match in the routing table. This IP
table lookup was easy in start but with unicast and multicast IP addresses the IP table
lookup was complex and require more time then before. CPU capabilities for computing
IP loo
kup table becomes limited and the bandwidth links were around 40 Gbps, which
causes the link to be unused due to low processing speed or complex computations.


Network infrastructure for data communication is divided in to Control plane and Data
plane. Co
ntrol plane comprises of routing protocols, table, Signalling protocols etc.
While Data plane forward packets between router and switches. Application specific
ICs are built to perform data plane forwarding packets that enable IP packets as well as
Label p
ackets at identical data rate. In order to utilize the unused links or avoid
congestion in the network can be done through implementing MPLS technology.


3.1

MPLS BENEFITS


This section will depict possible benefits as compare to IP, ATM and frame relay
tec
hnologies.


3.1.1

SINGLE NETWORK STRUCTURE


MPLS network
adhere

ingress LER to describe labels for incoming packets toward
egress LER through predefine criteria in network infrastructure. The reason for IP
emergence and dominance is because of current IP support

technologies development.
Integrating MPLS with IP we can exhibit better transport for the packet delivery. Layer
3 IP backbone can implement MPLS similar to ATM and frame relay at layer 2. MPLS
provide support for Point to Point Protocol (PPP), IPV4 and
IPV6, Ethernet and similar
layer 2 technology. Any transport over MPLS (AToM) mechanism allows routers to
switch layer 2 traffic without interfering about MPLS payload while using label
switching mechanism describe by MPLS

[9]
.


3.1.2

IP OVER MPLS


Previously IP

was deployed as layer 3 networking protocol due to its simplicity. ATM is
layer 2 protocol which offers end to end protocol connectivity but had limitations in ISP


20

WAN protocols. RFC 1483 implements IP over ATM to achieve multiprotocol
encapsulation over
ATM adaptation layer 5. This implementation requires IP mapping
and ATM end point to be configured manually. Another solution was an
implementation of layer 2 Ethernet LAN emulation at the Edge Router connecting the
network but this solution had limitation

in reliability and network scalability at ISP side.
The only possible solution was to make ATM switches intelligent enough to route label
switching technology with label distribution protocol and also to run IP routing Protocol
which was made possible thr
ough MPLS technology.


3.1.3

ISP PROTOCOL DEPENDANCY


In an ISP IP network, the forwarded traffic performs the destination IP address lookup
in the router to send the data to desire destination. If destination is external to ISP
network, which means an external

IP prefix exists in the routing table of every ISP
network router. Border Gateway Protocol (BGP) is responsible for both external
internet and customer prefixes so every router of an ISP network must depend upon
BGP protocol. While MPLS perform packet for
warding through label lookup only
associated with egress router. Thus the label contains information regarding the packet
for every intermediate router in the network instead of core router present at ISP
network. Only MPLS edge router need to run BGP to p
erform destination IP address
lookup to forward the packet in an ISP, IP network.


3.1.4

MPLS VPN MODEL


Virtual private network interconnects customer sites through common ISP network
infrastructure. ISPs are able to deploy either overly VPN model or peer to pe
er VPN
model. In an overlay model ISP provides point to point virtual circuits links between
customer routers at desire location. ISP is unaware of customer routes due to direct
peering routing between customer routers. The overlay model can be implemented

through IP network or frame relay switches at either locations implementing tunnelling
mechanism. In case of peer to peer model ISP routers participates in customer routing at
layer 3.


3.1.5

TRAFFIC ENGINEERING (TE)


It is a mechanism of achieving optimal use

of traffic resources and links which are left
unutilized due to network and protocol limitations. Internet technology and protocols
had proven to be worst in performance, congestion, bandwidth and link utilization, QoS
guarantee and path selection. MPLS i
mplements TE to control traffic flows between
congested nodes, allows path selection for unutilized paths or shortest path first, low
cost path mechanisms applied in IP routing. More detail about traffic engineering is
discussed in later sections.


3.2

MPLS AR
CHITECTURE


MPLS architecture consists of MPLS routers connected through mesh topology. MPLS
infrastructure network consists of following routers

[9
-
10]
.






21

3.2.1

INGRESS/EGRESS LABEL SWITCH ROUTER (LSR)



LSRs deployed at perimeter of MPLS network which provid
es an interface to inside
MPLS domain and to outside the IP network. The role of ingress/egress LSR is to insert
and remove labels when deployed as an ingress and egress. An ingress LER inserts label
on the data packet called as imposing LSR and forward it

towards egress LSR after
passing through number of hops where egress LSR removes the label called as
disposing LSR and forward it towards data link. These two routers are also known as
Provider Edge Routers.



3.2.2

INTERMEDIATE LABEL SWITCHING ROUTER


LSR ar
e devices present in MPLS domain to perform swapping, push and pop
operations of incoming and outgoing packets towards ingress/egress LSRs. They
receive an incoming label packets swap, push and pop labels perform packet switching
and forward it towards cor
rect data link.
The
packet forwarding mechanism based on
information present at each label.


3
.2.3

LABEL SWITCHING PATH (LSP)


It’s a sequence LSR path from ingress LSR followed by number of selectable
intermediate paths towards egress LSR. The figur
e depicts unidirectional LSP from
ingress LSR followed by three intermediate LSR towards egress LSR. If the packet has
already been labelled by ingress LSR then this case is called as nested LSP.























(
a
)





Egrees LSR





Ingrees LSR






Label Switch







22


























(b
)



Figure 3.1: LSP through an MPLS network




3
.2.4 MPLS LABELS


An MPLS label consists of 32 bits depicted in figure. The first label value consists of
120 bits followed by 3 experimental (exp) bits to control quality of services (QoS).
Bottom of stack

(BoS) identifies the number in the stack label, if it’s 0 which mean
bottom label stack otherwise if it’s 1 stack contain number of labels above the packets
so the stack can have one or more labels. First label in the stack is called top label while
the l
ast label is term as bottom label which is shown in figure
3.2
. Time to Live (TTL)
consists of 8 bits with the same functionality present in IP header. It avoids routing
loops by decreasing TTL value after traversing each successful hop. If TTL value in
la
bel becomes 0, packet is discarded.









Exp

BoS

TTL

Label

1

2

3 4 5 6 7 8 9 0 1 2 3 4

5 6 7 8 9 0 1 2 3 4 5 6 7 8 0 1

E
gress LSR

Label Switched Path

MPLS Networ
k

Ingress LSR




23


















Figure 3.2: Label


3
.2.5 FORWARD EQUIVALENCY CLASS (FEC)


This term is used in MPLS to allow same group of packets to follow along same path
and should be treated ide
ntically during packets forwarding. All the packets which
belong to same class have same level however in some cases they have different labels
if EXP have different value that will consider different forwarding mechanism due to
different FEC. Ingress LSR
decides packet forwarding based on FEC because it classify
labels in the initial stage

[10]
.


Layer 3 packets following towards destination IP address contain prefix, it might be
certain group of multicast packets or packets based on precedence or forward
ing
treatment, and also layer 3 IP address maintaining same BGP prefix and same next BGP
hop are some examples of Forwarding equivalency class.


3
.2.6 LSR OPERATIONAL MODES


There are three different modes of LSR during label distribution mechanism to o
ther
LSR.


a)

Label
D
istribution
M
ode


Its consists of downstream on demand label distribution mode in which every
LSR make request to the coming hop in a downstream LSR through LSP for
binding FEC. Single FEC binding is received by LSR through down streaming

LSR is upcoming hop describe in IP table. The other distribution mode is
downstream label distribution mode binds FEC distribution to nearby LSR,
where every LSR received binding information through neighbouring LSR.
Downstream on demand label distributio
n mode offer single binding while
unsolicited downstream gives multiple FEC bindings.





Label

Label

Exp

Exp

TTL

TTL

0

0

Label

Exp


1

TTL



24

b)

Label Retention M
ode


Liberal and conservative label retention modes are present. In case of liberal
label retention Label Information Base (LIB) maintains re
mote binding
information through down streaming or through upcoming hop. The label
binding is utilized in Label forwarding information base (LFIB) but no other
labels are kept which are not used for forwarding packets. The cause for storing
remote binding
in LFIB is subject to topological change and implementation of
dynamic routing due to downlink of router. Conservative label retention mode
configure on an LSR does not contain all remote bindings except an associated
upcoming hop in its LIB. However LLR w
ill help in rapid routing topological
change while CLR utilizes memory efficiently.



c)

LSP
C
ontrol
M
ode


In LSP control mode independent and ordered FEC bindings are performed.
FEC local binding is established independently by the LSR without involving
ot
her LSR and creating a specific FEC local binding according to FEC classes.
Ordered LSP binds FEC unless recognition is obtained through egress LSR or
label binding from an upcoming hop.



3.3

MPLS LABEL PACKET FORWARDING



In MPLS network label

packet forwarding has different phenomena then traditional IP
packet forwarding. We describe packet forwarding mechanism in a step by step
procedure

[11]
.


a)

Three main operations are performed in labels i.e. Push, Pop and Swap
. Figure
3.3

illustrates an

e
xample of push pop and swap. LSR determines according to
the LFIP information when label packet is received at LSR either top label
should be swap, pop and push. In label swap operation label 20 is replaced by
label 35 when it pass through LSR. During Pop
operation stack label 12 is
removed from the stack after passing through LSR. While in push operation
label 9 is inserted on the top of stack.
















20

35

9

7

5

IP

IP

IP

IP

IP

IP

12

8

9



25

b)

IP lookup is performed when IP packet is received at router while label lookup
is performing at t
he router through LFIB with particular Cisco Express
Forwarding (CEF) class. So router identifies an IP over label packet through
protocol information at layer 2 header. If CEF or LFIB forward the packet so it
can be unlabeled or labelled depending upon CE
F
-
IP lookup or LFIB
-
label
lookup. Both cases are shown in
Figure 3.4
.

In first case

CEF performs IP
lookup for an incoming IP packet at LSR that leads to two possible outcomes i.e.
IP
-
IP packet or IP
-
label packet respectively. In second case a label packet

is
received by the router so LFB performs label lookup and forward the packet
either label
-
IP or label
-
label respectively.



































Figure 3.4: CEF Lookup and LFIB Lookup



c)

Load balancing for desired label packets is performed by

Cisco IOS, these
packets may have same or different outgoing labels. Same label exist if the link
is between the link and routers belonging to label platform space but they are
different in case multiple upcoming LSR are present since upcoming LSR
IP

IP

IP

IP

IP

IP

16

23

14



26

indepen
dently provide labels. However IP over MPLS network offer packet
labelling procedure for MPLS domain and whenever packet leaves MPLS
network it becomes unlabelled.


d)

There are 0 to 15 labels reserved which LSR doesn’t use in normal cases to
forward packet
where label 0 stands for explicit null label and label three for
implicit null label. Implicit null label is assigned by egress LSR if label is not
assigned for FEC to accomplish pop label operation. Alert label is defined by
label 1 while OAM alert label
is used through label 14 that provides network
management operation and maintenance.


e)

Beside reserved labels, unreserved label are used to forward normal packets and
it consists of 20 bits, with the range of 16
-
10000 labels. They are significantly
enough
for normal labelling packet but if IGP prefixes are to be labelled we can
change the range to make them sufficient.


f)

Time to live (TTL) changes its values based on the label operation i.e. swap, pop
and push at each arriving LSR. In order to perform swap l
abel operation
incoming packet label TTL become equal to current label


1, for push label
operation the incoming packet label TTL becomes also label


1 and copied at
swap label. In

case of pop operation the incoming packet label TTL copies label


1 to e
xpose label.


g)

When LSR receives the packet with TTL equal to 1, it automatically drop that
packet and generate ICMP message for time expiry.


h)

Maximum Transmission unit (MTU) is present in IP packet which indicates
possible IP packet size sent through data

link layer. Similarly MTU in MPLS is
used for label packets and are bigger in size then IP packet since 4 bytes are
used for every label in addition to the packet. MTU default value is 1500 bytes
while MPLS MTU uses 1508 bytes including labels which are p
ossible to sent
over data link without any fragmentation processes.


3.4


CISCO EXPRESS FORWARDING


It is packet forwarding and switching mechanism specifically design for MPLS
networks. Basic functionality of the router is to forward packets towards the d
estination
through traversing addresses in IP table lookup and making decisions regarding next
hop i.e. switch or router. Every router has specific protocol to perform packet
forwarding mechanism and the information is stored in forward table. There are th
ree
basic ways in which routers forward the packets.


3.4.1

PROCESS SWITCHING



It is a slow process which involves routers to switch packets where Cisco IOS performs
packet application in CPU memory to perform destination IP lookup in IP tables .After
rece
iving result from IP lookup table packets are switch towards specific interface after
housekeeping for IP headers.TTL and CRC are recalculated during housekeeping.
Every IP packet forwarding information is present in the packets itself which routers
CPU pr
ocesses.



27


3.4.2

FAST SWITCHING


It is a switching mechanism based on demand forwarding. Process switching is
performed during the recipient of first packet to the destination while CPU built
and maintain the cache non as IP fast switching route cache to allow
identical
packets following the same destination. Although the cache is temporary and
depends on the time entries in that cache or add and deleted causing CPU
member free. Cache keep the entry records until packets are switch towards
same destination, how
ever these entries become unneeded and are deleted when
no packets following the same distinction are switch. Problem pertaining fast
switching occurs during prefix change related to routing table so cache entry
become invalid and the packet switching proc
ess entry needs to be built again
for route cache.


Due to demand building fast switching cache problems arise, the solution to avoid this
switching cache resulted in CEF switching. Now switching tables are not constructed
through demand rather they are b
uilt in advance such that every prefix has an entry in
routing tables and CEF switching table.CEF is necessary for MPLS networks because
router contains LFIB entries regarding the labels and IP packets which enter MPLS
domain are switch through CEF tables.

Despite of IP packet or label packets at LSR and
IP table lookup are CEF table lookup the resultant packet forwarding could be either
and IP packet are a label packet. CEF consist of two main data structures.


a)

Forward Information Base

b)

Adjacency Table


F
IB itself is CEF table which handles lawyer 3 forwarding and is identical to IP routing
table, even prefix entries are identical.FIB also contain information about IP prefix,
upcoming hop and connected interfaces .It also contain information for distance a
nd
matrix calculation based on specific protocol. While Adjacency Table manages
neighbouring devices through MAC layer 2 rewriting. In multi access enjoinment
dynamic device discovery mechanism is used by the routers through ARP that MAC
address to IP addr
ess.


IP packets are label through CEF table at ingress PE router while these IP packets
obtain more
than

one labels travelling through MPLS networks.LSR are capable of
inserting more labels only through LFIB functionality but cannot

use CEF table to
assi
gn labels
.

LDP,

RSVP or BGP are also capable of assigning labels through
recursion.


CEF load Balancing or Sharing is of significant importance for dynamic multi direction
links for forwarding IP are label packets and depends on maximum available path for
prefix. Per
-

packet load balancing offers balancing all the packets with round robin
technique. Per destination load balancing is default CEF scheme and performs hashing
functionality for source and destination address.







28























Figure 3.
5
: CEF

Table
and
Adjacency Table



3.5

TRAFFIC ENGINEERING
IN
MPLS


Traffic engineering has to minimise network congestions by modifying routing patterns
and exhibits traffic mapping streams with network resources that explicitly cause
reduction in congestion

and also it provides better quality service with latency packet
loss and jitter

[10]
. MPLS TE is implemented by extending IP protocol for forwarding
packets to decrease any failure caused in the network and increases efficient service
delivery. MPLS TE de
fines routing capabilities in its network by TE label switch path.

















Figure 3.6
:
TE label switching path


HOP 8

HOP
4

HOP
5




HOP 2

HOP 1

HOP 3

HOP 6

HOP 7

IP Rout ing
Prot ocols

IP R
out ing
Table (RIB)


CEF Table
(FIB)

Adjacency
Table



29


In figure

3.6,

there are multiple nodes from source hop 1 and hop 5 to destination hop 4
and 8. The traffic from hop 1 and 5 forwarded

to hop 4 explicitly routed from hop 2 and
3 while traffic from hop 1 and 5 forward towards hop 8 explicitly routed from hop 6 and
7. Hop 2, 3, 6 and 7 are LSRs offering LSP A, LSP B, LSP C and LSP D.




LSP
-
A: (
Hop
1

-

Hop
2

-

H
op3

-

H
op4)

Hop 1 and hop 4 ar
e ingress LSR and egress LSR while hop 2 and 3 are an
intermediate LSRs.




LSP
-
B:
(Hop5
-

Hop2
-

Hop3
-

Hop4)

Hop
5

and hop 4 are ingress LSR and egress LSR while hop 2 and 3 are an
intermediate LSRs.




LSP
-
C:
(Hop1


Hop6


Hop7


Hop8)

Hop
1 and hop 8

ar
e ingress LS
R and egress LSR while hop 6 and 7

are an
intermediate LSRs.




LSP
-
D:
(Hop5


Hop6


Hop7


Hop8)

Hop
5 and hop 8

are ingress LS
R and egress LSR while hop 6 and 7

are an
intermediate LSRs.


However IGP in IP networks will only compute smallest
path

or cost
towards source to
destination i.e. hop 1 to hop 4, hop1 to hop 8, hop
5 to hop 4 and hop 5 to hop 8. IGP
uses single metric to compute routing information which may be acceptable for very
simple network but internet is complex networks of hops

so MPLS TE will provide
better routing capabilities through constrain based routing mechanism. MPLS TE
routing mechanism follow certain constraints on LSRs for computing path towards
ending LSRs to forward packets through TE LSP.


3.6

MPLS TE OPERATIONS


The
re are four main operations performed in MPLS TE.



3
.6.1

LINK INFORMATION DISTRIBUTION


It extends IP link state with distributed topology information since LSR implementing
constraint base routing should know current extending link list and its attribute
s for
implementing those constraints in path selection. OSPF and IS
-
IS are two link base
protocols that offers capabilities for distributing attributes where LSR develop TE
database apart from normal topological database based on these capabilities. MPLS T
E
also increments bandwidth availability

attribute with 8 priority levels are describe for
TE LSPs,
TE metric
attribute is used for optimizing paths identical to link metric in
IGP,
and
administrative group attributes enforces inclusive an exclusive rules.




3
.6.2 COMPUTING PATHS


TE LSP develops a TE topological database to perform CBR along with shortest path
first algorithm. Both work in integration to implement CSPF algorithm to determine


30

shortest path and optimal path approximation but are unabl
e to guarantee optimal traffic
mapping stream for network resources.


3
.6.3
TE LSPs SIGNALING


MPLS TE signals LSP through RSVP by introducing following objects.


a)

LABEL_REQUEST

It is used to bind label at every hop.



b)

LABEL

It is used for Resv message dis
tribution.


c)

EXPLICIT_ROUTE

It define explicit hop list for signalling.


d)

RECORD_ROUTE

This object gather label and hop information during signalling path.


e)

SESSION_ATTRIBUTE

It defines LSP attribute requirement such as protection, priority etc.



3.7


B
ASIC MP
LS DEVICE AND INTERFACES


MPLS devices
maybe

IP

routers, ATM switches or multiservice switches. However
multiservice switch is best selection among the devices because it offers
service
connectivity
with IP, MPLS, frame relay, Ethernet, X.25, and TDM.

MPLS

interface
configuration include IP routing, IGP routing protocol along with TE i.e. ISIS
-
TE and
OSPF
-
TE however IGP routing protocol implementation is not necessary while static
routes are used, EGP protocol implementation in case of autonomous system, an
d LDP
or RSVP signalling protocols.


3.8

MPLS OPERATIONAL MODES


There are two MPLS operational modes


a)

Frame M
ode

In this operational mode packets are labelled and exchanged in frames at layer 2
to work through unicast IP destination routing. In MPLS data pl
ane, three tasks
are performed
.





Ingress router perform FEC classification over received IP packet and stack the
label corresponding with FEC while in destination based unicast IP routing FEC
refers to subnet destination and layer 3 lookup is in the forwa
rd table is
performed for packet classification.




Intermediate LSR then perform lookup in label forwarding table for inbound
label and outbound label of incoming packet with respect to similar FEC i.e. IP
subnet.



31



The label packet received for similar FEC a
t egress router removes the label
through layer 3 lookup which produces an IP packet.


Label binding in frame mode is implemented through IP subnet and MPLS labels for
unicast destination based routing with the help of Tag distribution protocol (TDP) and
l
abel distribution protocols (LDP).


b)

Cell Mode

In MPLS cell mode ATM LSRs forward cells instead of packets, similarly
ingress router perform forwarding table lookup assign label to a packet. Each
packet is segmented to form different cells while every cell

VPI/VCI will get a
label value. These cells are forwarded through intermediate LSRs based on the
LFIB information. ATM LSR
manages

cells individually and cells with
VPN/VCI label values

are sent towards upcoming hop.

At the edge of MPLS
domain, egress rou
ter performs re
-
segmentation to form a frame.









32





Chapter
4

IP Networks



33

Rapid growth in the network technology emerge computer systems to communicate
through protocols. Computers systems become connected through physical and logical
transmission
media to share information among the networks. Before single computer
centre existed and the concept was completely change with organization needs to
interconnect multiple computers for processing and storing data share information and
running Clint server

application on the systems, which is resulted in the formation
computers networks. In a computer world the connection is establish between two
autonomous systems for exchanging information connected through some transmission
medium i.e. fibre, copper, mic
rowaves, and satellites etc. Computer network consist of
actual machine with similar /different operation systems running some programs and
performs some operation through interconnection

[12].



Computers networks are required for business application i.e
. sharing same resources,
storing data and databases, accessing printer and scanning devices, running client server
applications; for home application i.e. e
-
commerce, person to person, multimedia and
interactive entitlement which constitute of newspaper,
history, information, hobbies,
health, support,

research, sms, chat rooms, video on demand, movies and television
programs, product sale/ purchase, etc; for mobile users i.e. pads and note book
connective to be able to access internet services during motil
ities, etc.


In an internet, computer networks consist of number of interconnected devices i.e.
router, switches, servers, end nodes and they need common protocol mechanism to
performs communication.OSI defines seven layers for the communication mechanism
whereas internets implements TCP/IP protocols to establish communication path and
performs data transmission. Point to point and broadcast link transmission mechanism
are used

[13]
. In broadcast network all the machine share single channel for
communicat
ion while point to point network maintain individual connectivity between
the devices. Short messages i.e. IP packets are sent from source to destination entertain
by single/multiple routers and switches. IP packet contain destination address of the
packet
s but in case of broadcast network all the packets are deliver to all the nodes
connected to the network through using broadcasting code in the address field,
multicasting occurs when IP packet are sent to a subset of nodes. In point to point
networks uni
casting is performed since they is single sender node and single recipient
node

[14]
.


4.1

IP
STANDARD ARCHITECTURE


Traditional centralized IP network consist of large centralized processor connected with
two terminals at either sides or computing resour
ces. Internet contains an infrastructure
of core routers connected through Tetra byte fibre optic transmission medium. The core
routers provide link to ISPs or enterprise network through T3 line of Giga byte
transmission such that ISPs connect common busin
ess, homes and other ISPs with local
area network, or metropolitan area network.LAN consist of small number of networks


34

nodes connected through ether net and consist of bus, ring, star, mesh etc topologies .

B
us and token ring topologies form a broadcast n
etwork. MEN encircle cities through
simple bus topology connected either through Ethernet or wireless access; cable TV is
an example of MAN network. WAN covers larger geographic area i.e. countries, or
continents. Larger ISPs are often consist of WAN netwo
rks and involves
communication subnet to carry transmission lines and performs switches for end nodes
running application programs at the user premises. Transmission lines consist of high
speed cannel i.e. fibre optic, copper, radio links, whereas switchin
g is performed
through specialized computers which connect these lines across countries/continents.
Since there are different types of networks which connects nodes and other networks, in
order to perform transmission between nodes of different types of ne
tworks gateways
are required to connect them and performs hardware software translation, this
mechanism is called internet or network

[12]
.




























Home

Karlskrona

MAN

Bus Topology

Star Topology

Ring Topology

Subnet



35

Figure 4.1
:

Generalized Internet / ISP Architecture


In Connection oriented communicatio
n architectures model network offers service
through establishing connection before data transmission. PSTN is common example
when receiver receives the calls it replies and end to end connection is establish through
switching offices. Data follows in a se
quential manner along in the path between source
and destination. In data network TCP provide connection oriented services with quality
and reliable of data transmission. Connection less architecture operates similar to post
system in which source and dest
ination addresses are present. Network devices use
information attached to the packet and independently route the packet towards
destination address. Connectionless transmissions depend on best efforts data
transmission and do not provide guarantee QoS. So

packet may deliver un
-
sequentially
with delay va
riations, and may also be lost during transmission

[15
-
16]
.


4.2


I
nternet Protocol



IP was developed to transmit internet data gram from source to destination by passing
through interconnected system and n
etwork devices. Data gram is a bulk of data
transmitting through connectionless network its transmission is analogous. An IP data
gram of email message consist of data gram length and addition of information header
implemented by TCP or TCP header forward
the packet to the routers along with 802.3
frame header

[17]
, router take off the frame header and forward data gram, check for
destination IP address and forward the data gram towards the destination IP address. In
case of virtual circuit connection a con
nection oriented mechanism, first the destination
address is concerned and desired path is establish performed data transmission. After a
change of information the path is realised by realising the network resources. Since IP is
connectionless protocol whi
le TCP is connection oriented protocol, by integrating two
protocols we can converge between reliability and unreliability of data transmission

[12]
.


4.2.1

Data gram Fragmentation/Defragmentation

IP deal with fragmentation and defragmentation during data

gram transmission by IP
address to ensure that data gram reached the correct destination address; this is how IP
provide address consistency. IP data gram fragmentation and defragmentation is
mandatory in some cases when data gram frame sizes are differen
t with respect to LAN
or WAN.








36













Figure
4
.1
:
IP Datagram


4.2.2

IP Header


IP header have 20 octets for control information, IP version is defined with Version (4
bits), IP header is 32 bits words measure through internet header length (IHL
), IHL also
measured offset, 8 bits of types of service defines required data gram QoS. Real time
application like voice and video QoS is required to set a priority for voice datagram
samples and therefore assure packet delivery and reliability. In one typ
es of service
fields is describe for voice and video application, total length field (16 bits) calculate IP
datagram in octets up to 65,535.Fragmenatation offset consist of 8 bits if data packet are
different in sizes LAN and WAN fragmentation is performe
d on large IP datagram
called fragments to fit in the communication traffic capacity and are reassemble at the
destination node.16 bit identification field is use to reassemble the datagram from the
fragments, this field contain 3 flags values; if bit 0 is

set 0 which mean “reserve” , if bit
1 set to 0 it mean “may fragment” and if set to 1 which means “don’t fragment”,
similarly if bit 2 is set to 0 it mean “last fragment” and if set to 1 means “more
fragment”. the 13 bit fragment offset links the fragm
ent to a complete message .Time to
live 8bits measures the time of datagram within the internet while if TTL is equal to 0
then datagram is destroyed is measured in second or per hops. The maximum TTL for
datagram is 225 second while 64 is a default valu
e used in many systems. Trace route
and ping commands are used for diagnosing TTL.8 bits protocol fields identifies
higher layer protocols i.e. UDP TCP and ICMP.16 bits header checksum performs
integrate check on the receiving data pack.32 bits source ad
dress identifies 32 bits
source address of the network node while 32 bit destination address locate the IP
destination of the network node.32 bits option and padding fields is of variable length
and contains datagram information as well as stream identifie
r, source routing, time
stamp and security information

[17]
.




37
















Figure
4
.2
:
IP Header



4.3

I
ntranet work Routing Communication

IP datagram consist of 32 bits address per source and destination identification but in
the communication chann
el internet work of datagram may perform and the
intermediate devices i.e. routers manipulate information to identify destination address
in their routing tables to forwards datagram to correct circuits, however due to change in
network topology circuits m
ight fail due to congestion.


Router perform some function on incoming packets by correcting destination address
efficiently through routing table information and forwarding table and makes optimize
paths available for each packets .forwarding table can
be built manually or can perform
packet forwarding mechanism dynamically based on adjacent routers and network
topology constants. static routes are easy to construct but difficult to maintain because
for same sources and destinations with packet flow with

specify path which reduce
efficiency bandwidth and resource utilization, can cause congestion and link /node
failures due to continuous constant transmission between static routes, and some portion
of the network resources still be unutilized. Static rou
tes are not the correct solution for
better quality of service, resource utilization and reliable transmission of data packet as
compared to dynamic routing

[13]
.


Dynamic routing is implemented to better to accept changes in network by running
different p
rotocols and algorithms to use metrics for finding shortest distance from
source to destination. The metric parameters can based on shortest path or list cast
between the end points .link state algorithms makes decision based on links which
connects the no
des in the network. Distance vector algorithms measures smallest
0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9 0 1

Bits

1

1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3



38

distance between source and destination to transmit datagram. Routers implements links
state algorithms and distance vector algorithms in intranet work communication. IGPs
use these algorithm
s while routing information protocol (RIP) implements DV
algorithms. OSPF is also an IGP decide routes through like state algorithms.


4.4

R
outing Information Protocol



RIP is used for integrate way communication, he uses distance vector algorithms in

which routers exchange information through its routing table periodically. The path
form source to destination is determined as a best path which contains less number of
hops. The protocol implementation is such that many LAN OS itself implements RIP so
i
t gives interoperability problems along with allowing only 50 hops path length which is
less a number, Routing loops are present internetworks because its requires more time
to get a updated routing information .All the devices running RIP must have RIP dr
iven
routing table contain destination IP address a matrix per calculating cast next router
address and a flag value.RIP packets exchange routing information by transmitting
message from 522 UDP port

[18]
.



















Figure
4
.3
:
RIP Header



The p
acket format of RIP in which first 8 bits (Command).Command field takes
following values:



0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
7 8 9 0 1

Bits

1

1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3



39


1

It request for information in the routing table

2

Receive reply from the routing table

3

Trace on

4

Trace off

5

Sun micro system has reserve this value

9

To update the request

10

To update response

11

To update acknowledge


Next 8 bits contain “Version”, which is version number of RIP. Next 16 bits must be 0
then 16 bits identifier; again next 16 bits must be 0. The RIP packets have routing
information

entries i.e. destination IP address and metric. Metric entry obtains normal
values from 1 to 15 but if the entry becomes 16 then destination address become
unreachable. RIP facilities 25 entries per routing information along with datagram
.RIP
V2 [18]
prov
ides additional security to RIP messages and is almost identical 2 original
format 2 only the “version” field contains V2 while command, IP address, metric, field,
address family identifier are similar. There is a route tag field to preserve route
informa
tion i.e. internetwork or intra net. A subnet mask field consist of 24 bits and
provide an association with routing entries, a next hop field also consist of 32 bits and
provide IP address next hop in the routing entry.


RIP is implemented in WAN circuits